Thaddeus Thawne is a clone of Bart Allen, and was created in the 30th century by Bart's maternal grandfather, President Thawne. Thawne, being the descendant of the Flash's enemy Professor Zoom, got tired of his grandson's crime fighting activities in the 20th century and decided to create a clone of Bart using more Thawne blood so that he would be more ruthless. His mission as the "Reverse-Impulse" was to go back in time and replace Bart, but he was easily defeated twice.
In his second attempt, upon realising Impulse was prepared to sacrifice himself to save Max Mercury, he fled, apparently horrified by the contrast between Bart's adopted family and his own grandfather's treatment of him as a weapon.

Thaddeus Thawne is a clone of Bart Allen, and was created in the 30th century by Bart's maternal grandfather, President Thawne. Thawne, being the descendant of the Flash's enemy Professor Zoom, got tired of his grandson's crime fighting activities in the 20th century and decided to create a clone of Bart using more Thawne blood so that he would be more ruthless. His mission as the "Reverse-Impulse" was to go back in time and replace Bart, but he was easily defeated twice.
In his second attempt, upon realising Impulse was prepared to sacrifice himself to save Max Mercury, he fled, apparently horrified by the contrast between Bart's adopted family and his own grandfather's treatment of him as a weapon.
Inertia has recently surfaced in both the Flash: The Fastest Man Alive and Teen Titans. Because Flash now contains the Speed Force within him, Inertia is forced to use drugs to obtain his super speed

Thaddeus Thawne is a clone of Bart Allen, and was created in the 30th century by Bart's maternal grandfather, President Thawne. Thawne, being the descendant of the Flash's enemy Professor Zoom, got tired of his grandson's crime fighting activities in the 20th century and decided to create a clone of Bart using more Thawne blood so that he would be more ruthless. His mission as the "Reverse-Impulse" was to go back in time and replace Bart, but he was easily defeated twice.
In his second attempt, upon realising Impulse was prepared to sacrifice himself to save Max Mercury, he fled, apparently horrified by the contrast between Bart's adopted family and his own grandfather's treatment of him as a weapon.